Swallowing is a complex behaviour in which the output of an integrative brainstem network gives rise to a patterned movement sequence described as the pharyngeal stage of swallowing. While several lines of evidence have demonstrated the importance of oropharyngeal sensory inputs in activating this medullary swallowing network, the range of afferent patterns that are both necessary and sufficient to evoke swallowing has not been fully elucidated. Stimulation of receptive fields innervated by the superior laryngeal nerve (SLN) or the pharyngeal branch of the glossopharyngeal nerve (GPNph) appear to be particularly effective in evoking or modulating the pharyngeal swallow; these “reflexogenic” areas correspond to the laryngeal mucosa, including the epiglottis and arytenoids, the lateral pharyngeal wall, posterior tonsillar pillar and peritonsillar areas.
In humans, the anterior faucial pillar historically has been considered the most reflexogenic site for swallowing. However, the recent finding that the pharyngeal swallow may begin after the bolus head passes the anterior faucial pillars in healthy adults, including geriatric adults, suggests that stimulation of more posterior pharyngeal regions may be required to elicit swallowing. The importance of more posterior oropharyngeal areas in swallowing elicitation is also suggested by anatomic evidence that the human posterior tonsillar pillar, as well as discrete regions of the palate, pharynx and epiglottis are innervated by a dense plexus formed from the GPNph and the vagus nerve. The spatial correspondence between these areas of dual vagal/GPNph innervation and reflexogenic areas for swallowing has lead to the hypothesis that swallowing is elicited most readily by stimulation of areas innervated by both the GPNph and vagus. Dynamic stimuli that excite primary afferents within a number of receptive fields over time appear to elicit swallowing more readily than do static stimuli.
A variety of stimulus modalities have been applied in attempts to evoke swallowing. Repetitive electrical stimulation of the SLN or the GPN, particularly at stimulation frequencies between 30 and 50 Hz, evokes swallowing in a number of animal species. This suggests that the repetitive nature of the stimulus, and the repetition rate, are critical variables in swallowing elicitation. More recently, electrical stimulation of the pharynx has been reported to increase both the excitability and size of the pharyngeal motor cortex representation in humans, and facilitate swallowing in dysphagic patients following stroke. Mechanical and chemical stimuli can evoke swallowing in animal species. In humans, reports on the effects of cold mechanical stimulation of the anterior tonsillar pillar have been variable, some authors reporting decreases in swallowing latency and increases in swallowing frequency, and others failing to find an effect of this type of stimulation on oropharyngeal bolus transit, esophageal coordination, or the temporal pattern of swallowing. Three studies have examined the effects of cold mechanical stimulation applied to the anterior tonsillar pillars in small samples of dysphagic stroke patients. They reported a short-term facilitation of swallowing, measured in terms of reduced delay of the pharyngeal swallow, in some patients, with no related reduction in aspiration. Longitudinal studies, examining the potential long-term effects of oropharyngeal sensitisation on not only swallowing physiology but also on nutritional and respiratory health, have not been reported. Reports on the effects of gustatory stimuli also have been variable. A sour bolus has been reported to facilitate swallowing in stroke patients. Whereas some authors have reported that swallowing latency is significantly reduced by a combination of mechanical, cold, and gustatory (sour) stimulation, others have reported that a cold plus sour bolus reduces the speed of swallowing.
Prior art research shows a novel method for determining laryngopharyngeal sensory thresholds using trains of discrete air pulses delivered endoscopically to the mucosa of the pyriform sinuses and aryepiglottic folds. Sensory thresholds are calculated through psychophysical testing and from elicitation of the laryngeal adduction reflex. The air-pulse train is an interesting stimulus in that it has many of the properties that appear crucial in evoking the pharyngeal swallow. For example, a single air pulse is a dynamic stimulus that could be applied to a number of receptive fields including regions innervated by both the GPNph and SLN. Furthermore, an air-pulse train represents a repetitive stimulus that can be applied at specific frequencies and pressures.
Accordingly, it would be advantageous to provide an oral device that can deliver air-pulse trains to the oral, oropharyngeal or peritonsillar areas. Further it would be advantageous to provide an oral device that facilitates and/or elicits swallowing in adults and children. As well, it would be advantageous to provide an oral device that can provide visual and/or audio feedback responsive to a swallowing attempt. In addition, it would be advantageous to provide an oral device that may be used to improve the motor integrity (e.g., strength, control, tone, accuracy) of the lips, tongue, and/or soft palate, with associated improvements in swallowing, as well as speech production and speech intelligibility.
In addition, recent studies have suggested that the air-pulse train delivered to the oral or oropharyngeal areas results in laryngeal elevation, in some cases associated with a swallow proper. Thus, is would be advantageous to provide an oral device that facilitates or evokes laryngeal movements, such as elevation movements, since laryngeal movement may be a precursor to a swallow proper. It is also clear from previous studies that delivery of an air bolus into the mouth is not the only way in which laryngeal elevation can be achieved. A well-known therapeutic maneuver in swallowing rehabilitation is the ‘effortful swallow’ in which the patient is simply instructed to swallow effortfully by contracting his/her muscles maximally. This has been shown to result in a more efficient, safer swallow. It has recently been shown that an effortful swallow is associated with increased laryngeal movement. This laryngeal movement can be recorded from a transducer worn around the neck. The amplitude of the output signal from the laryngeal transducer, representing laryngeal movement, is significantly greater in association with an “effortful” swallow, compared to a normal swallow. Other therapeutic maneuvers that also result in increased laryngeal movement include the Mendelsohn Maneuver, supraglottic swallow, super-supraglottic swallow, and the Shaker exercise.
Accordingly it would be advantageous to provide a feedback system that can provide the patient and clinician information about the physiologic correlates of these compensatory swallowing maneuvers, and similar maneuvers that produce laryngeal movement patterns. Certain speech exercises also give rise to laryngeal movement. For example, the pharyngeal squeeze involves producing a vowel sound at a high pitch. This elevates the larynx while at the same time maximally recruiting the pharyngeal muscles. Thus, it is used to strengthen the pharyngeal musculature. Accordingly, it would be advantageous to provide a feedback system that could provide information to the patient and clinician about the laryngeal movement associated with these speech therapy exercises.